My character's resistance is listed on the details pane when I open my inventory, and it's a simple integer. It appears to undergo some type of calculation to determine the percentage of damage each of these actually counts for:

Judging by the tooltip, there's some factor based on enemy (and/or my?) level. I believe these numbers are 80 due to my intelligence - I had 798 at the time this was taken.

How is percentage resistance calculated? Although the base "Resistance" integer appears to be derived directly from my stats, does the percentage in this tooltip take into account skills, enchantments, or other modifiers that change resistance?

I'm pretty sure the percentage takes into account only the raw resistance, in the same way as damage reduction from armor takes into account only the armor. Don't know the formula, though.
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OakMay 24 '12 at 16:01

It's the same formula as armor, but differs by a scale factor (this is why 1 armor from Strength gives the same defensive benefit as .1 resistance from Int (unfortunately, only armor is considered in the items' "protection" stats).
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Raven Dreamer♦May 24 '12 at 16:37

In addition to all those tables people posted here, you may want to have a look at a graphed version of resistance vs damage reduction: fooplot.com/…
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fjdumontJul 16 '12 at 11:52

Beat me to it! This post on the Diablo 3 forums also has a pretty good discussion about armor and resistances.
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SternoMay 24 '12 at 16:16

"Each point of resistance goes further at a lower level than a higher one" - well, yeah, the same way 100 armor goes further at a lower level than at a higher one...
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Raven Dreamer♦May 24 '12 at 16:35

Thank you, this is precisely the information I was seeking.
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agent86May 25 '12 at 13:37

2

The 0.07% is an error due to using the stated resistance stat. If instead of using the 80 that it shows, you use 79.8 (int*.1) the final result comes out to 31.94555% which is much closer. However, this suggests that there may be subtle rounding or play in other parts such as possibly the Intelligence score.
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user27179Jun 7 '12 at 4:09

Probably worth clarifying that modifiers that change resistance will be included in the tooltip, however effects that directly reduce damage taken won't, as the tooltip only deals with resistance-based damage reduction.
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CataleptJun 7 '12 at 4:24

This list does not include legendaries and other skills / abilities. Generally speaking you can reach 930 All Reistance and add another 690 of a specific resistance for a total of 1620. This translates into about 83-85% damage reduction in Inferno, see: how is resistance percentage calculated